Sift flours and sugar into bowl, rub in butter. Add egg and enough water to make ingredients cling together. Press dough into a ball, knead on floured surface until smooth. Cover, refrigerate 30 minutes.
Preheat oven to 200°C (180°C fan-forced).
Roll dough on floured surface until large enough to line 23cm pie plate. Lift pastry into pie plate, gently ease into side of plate, trim edge.
Place pie plate on oven tray, line pastry with baking paper, fill with dried beans or rice. Bake 10 minutes. Remove paper and beans, bake further 10 minutes or until pastry is browned lightly, cool.
Meanwhile make custard filling Whisk eggs, extract and sugar in bowl until combined. Heat milk until hot, quickly whisk into egg mixture.
Pour custard into pastry case, bake 15 minutes. Sprinkle custard evenly with nutmeg, bake further 15 minutes or until custard is just set, cool. Refrigerate until cold.
Recipe can be made a day ahead and stored, covered, in the refrigerator.